1. Field of the Invention
The present invention relates to an improved process for the preparation of unsaturated long-chain aliphatic secondary amines by reducing unsaturated long-chain aliphatic nitriles with hydrogen.
2. Description of the Related Art
Amines having long-chain alkyl groups are generally prepared by reducing long-chain aliphatic nitriles, derived from natural fats and oils, with hydrogen. When long-chain aliphatic nitriles are reduced with hydrogen, a mixture of primary, secondary, and tertiary amines are obtained. Among these amines, unsaturated long-chain aliphatic secondary amines are advantageous in that the quaternary ammonium salts thereof can provide softness and antistaticity to various fabrics and hair, and in addition, can be used as a softener for providing excellent water absorbability and handling ease to the treated fabrics. Therefore, a process for selectively preparing secondary amines at a high yield is desired.
Known processes for the preparation of unsaturated long-chain aliphatic secondary amines are the reduction of unsaturated long-chain aliphatic nitriles with hydrogen using a Cu-Cr catalyst (BP 773,432) or an Ni hydrogenation catalyst (USP 2,355,356, USP 2,784,232, BP 759,291, Japan Kokai 55-9018). The former process has a disadvantage in that a longer reaction time is necessary because of the low activity of the Cu-Cr catalyst, and the latter process gives only a poor selectivity of unsaturated long-chain aliphatic secondary amines because most of the unsaturated bonds in aliphatic chains are hydrogenated while the nitrile radicals are converted to amino radicals.